The present invention is directed to the field of power driven wheelchairs, in general, and more particularly, to a method and apparatus for setting speed/response performance parameters thereof to the operational capabilities of an individual user.
Power driven wheelchairs which may be of the type manufactured by Invacare Corporation of Elyria, Ohio, for example, generally include right and left side drive wheels driven by a motor controller via respectively corresponding right and left side drive motors, all of which being disposed on the wheelchair. An exemplary illustration of such a motor drive arrangement is shown in the schematic of FIG. 1. Referring to FIG. 1, a motor drive controller 10 which may be an Invacare MK IV™ controller, for example, controls drive motors 12 and 14 which are mechanically linked respectively to the right side and left side drive wheels of the wheelchair. A user interface 16 which may include a joystick 18 and selection switches (not shown) operable by a user is also disposed on the wheelchair in a convenient location to the user. The user interface 16 is generally interfaced to the controller 10 over a two wire serial coupling 20 to permit the user to select a drive program appropriate for operating the wheelchair in its environment and to adjust the direction and speed of the wheelchair within the selected drive program. The controller 10 may be programmed with a plurality of drive programs, each suited for a particular operating environment.
The motor controller 10 is generally powered by a battery source 22, which may be 24 volts, for example, also disposed on the wheelchair. The drive motors 12 and 14 may be of the permanent magnet type and may be either a gearless, brushless AC motor or a brush type DC motor. The controller 10 may include a microcontroller interfaced and responsive to the user interface 16 to control drive signals 24 and 26 to motors 12 and 14, respectively, via a power switching arrangement configured in accordance with the motor type being driven. The power switching arrangement may be powered by the 24V battery 22. Thus, as the user adjusts the speed and direction of the wheelchair via the joystick of interface 16, appropriate drive signals 24 and 26 are controlled by controller 10 to drive the motors 12 and 14 accordingly. Controller 10 generally controls motor speed to the user setting in a closed loop manner.
Actual speed of each motor 12 and 14 is derived from signals 28 and 30 respectively sensed therefrom. For example, for AC motors, a Hall Effect sensor may be disposed at the motor for sensing and generating a signal representative of angular position. The controller 10 may derive motor speed from a change in angular position for use as the actual speed feedback signal for the closed loop speed control of the motor. For DC motors, the voltage Va across the armature and armature current Ia may be sensed from each motor 12 and 14 and provided to the controller 10 via lines 28 and 30, respectively. Controller 10 may in turn derive the actual speed of each motor 12 and 14 from the respective voltage Va and current Ia measurements thereof for use as the speed feedback signal for the respective closed loop speed control of each motor 12 and 14.
For safety purposes, certain performance parameters of the wheelchair which may include, but not be limited to, forward speed, turning speed, reverse speed, response, forward acceleration, turning acceleration, turning deceleration, torque and braking (forward and reverse deceleration), for example, are preset during manufacture and stored in a non-volatile memory 32, which may be an electrically erasable programmable read only memory (EEPROM), for example. The motor controller 10 is constrained in its control of the drive motors by these performance parameters. However, these factory preset performance parameters are established for an average user and are not meant to satisfy the safety needs and operating capabilities of all users. So, the wheelchair manufacturer stores the average performance parameters in a non-volatile memory which is alterable in the field, like the EEPROM.
When a power driven wheelchair is sold to a user at a dealership, for example, before the user may be allowed to operate the wheelchair unattended, a trained medical health adviser works with the user to determine safe performance parameters for the user based on the user's cognitive response and physical limitations, like tremors, arthritis, . . . etc. Currently, each of the aforementioned performance parameters is individually determined to satisfy each user's needs. Once determined, each of the new performance parameters is entered into the non-volatile memory 32 of the controller 10 through a remote programmer 34 which may be electrically coupled to a port of the microcontroller of controller 10 via signal lines 36, for example, thus, rendering the wheelchair unique to the user's safe operating capabilities. Each dealer is generally provided with one or more remote programmers. Each remote programmer 34 may include a screen 38 for displaying interactive text and graphics and a plurality of pushbuttons 40 for communicating with the microcontroller which is programmed to interact with the programmer 34 and EEPROM 32 as will become more evident from the description found herein below.
Determining each safe performance parameter for a user may require an iterative procedure. That is, a user may first operate the wheelchair with a preset performance parameter, like forward speed, for example, under the observation of the medical adviser. If the user operation is found unacceptable, then a new parameter setting is entered into the controller via the programmer and the user operates the wheelchair with the newly entered parameter. From the observations, the medical adviser may re-adjust the parameter setting to better suit the user's operating capabilities and the procedure is repeated until the medical adviser is satisfied that the parameter setting is safely within the user's operational capabilities. This iterative procedure will continue individually for each performance parameter for a drive program and the process is repeated for each drive program of the controller.
Understandably, the determination of the individual performance parameters currently performed is a very timely and costly operation which needs improvement. The present invention is intended to address the timeliness and cost of the current parameter setting technique and provide a method and apparatus which overcomes the drawbacks thereof.